1. Field of the Invention
The present invention relates to a sliding gate nozzle showing stable durability in use for special steel, particularly Ca alloy-deoxidized steels.
2. Prior Art
As a plate for a sliding gate nozzle for controlling a molten steel flow in continuous casting of molten steel, alumina-carbon refractories have been used widely in recent years to prevent fuming due to pitch, which has conventionally been used in the plate, in order to achieve higher durability and service environments.
However, with the increasing demand for steels of higher quality, the addition of special alloys to molten steel and chemical treatments of the molten steel have come into practice, which has led to severe corrosion of the plate for the sliding gate nozzle at the sliding surface of the upper plate, particularly when molten steel deoxidized with Ca alloy is applied thereto.
To cope with this problem, use of zirconia-based materials has been proposed, as for instance disclosed in Japanese Patent Application Kokai Nos. 60-77162, 46-7857 and 59-61567.
A sliding gate nozzle plate of a zirconia-based material, however, lacks stability in spalling resistance and, therefore, does not promise satisfactory durability of the sliding gate nozzle for receiving a melt of special steel, particularly a molten steel deoxidized with Ca alloy.